Editorial Commentary: Decreased hip ligament thickness in patients with dysplasia may contribute to hip instability, above and beyond associated acetabular under coverage.

ABSTRACT

Hip dysplasia is a pathomorphological deformity that leads to decreased acetabular coverage and hip instability. Many different radiographic measurements have been explored to characterize hip dysplasia, including the lateral center edge angle (LCEA), femoro-epiphyseal acetabular roof (FEAR) index, and Tonnis angle. Magnetic resonance imaging (MRI) offers three-dimensional characterization of the hip pathomorphology that may be more detailed than two-dimensional radiographs, as well as a modality that is free of radiation. Recent research shows that dysplastic hips are associated with significantly thinner ligament thickness compared to non-dysplastic hips. The iliofemoral ligament (IFL) is the most important hip capsular structure and helps to stabilize the hip joint, particularly in hip extension and external rotation. Differences in IFL thickness may help to explain why those with dysplasia are more prone to hip instability, above and beyond their acetabular under coverage. This reiterates the need for routine capsular closure and/or plication in patients with femoroacetabular impingement syndrome in order to prevent further instability.